De Pradt and Napoleon

Thesis (M.A.)--University of Kansas, History, 1932

Investigating the attitude towards ambiguity: Interindividual differences in automatic activations of evaluations of ambiguity

Direct measures of (in)tolerance of ambiguity provided evidence for a variation in liking of ambiguity. Given the limitations of these measures, we developed a direct measure of attitude towards ambiguity. However, the main part of this thesis deals with the questions, whether there are interindividual differences in the automatic activations of evaluations of subjective ambiguity (single information triggers multiple distinct representations). We developed a database with norms for ambiguous and unambiguous German words. A subset of these words matched for several dimensions was used in two indirect measures. The Implicit Association Test (IAT) assessed the relative strength of associations of ambiguity and clearness with positive and negative valence, respectively. In the Evaluative Priming (EP) paradigm ambiguous and unambiguous primes preceded targets with positive or negative valence. This allows to draw inference about the automatic evaluations of the primes. In order to validate potential variances in the automatic evaluations of the primes (indicated by interindividual differences in latencies as a function of prime type and target type), information about the attitude towards ambiguity was used as a moderator. Apart from the first study, which investigated the relation of direct measures with the IAT and showed unrelatedness, all other studies used the EP paradigm, using either the IAT score (studies 2 – 4) or the induced associations of opposite valence with ambiguity and clearness (studies 5 – 6) as moderators. Studies 2 and 3 provided evidence for interindividual differences in the activation of evaluations of ambiguity via a three-way interaction of prime type, target type and IAT score. However, this three-way interaction was not found in the replication study 4. In study 5, there was an interaction of prime type, target type, and induction but opposite to the expected direction. The post-hoc explanation for the partial contrast effect was further investigated by manipulating the SOA in study 6. However, in this study the induction had no influence on latencies in the EP paradigm, but there was a prime type, target type and SOA interaction. This can be explained in terms of contrast (long SOA) and assimilation (short SOA) effects if we consider the evidence across the aforementioned studies showing that, on average, participants had a stronger association of ambiguity with negative valence and clearness with positive valence. Summarized, evidence for interindividual different automatic evaluations of ambiguity was weak, but the results of the EP paradigms indicated a more negative (or less positive) automatic evaluation of ambiguity compared to clearness. The implications of automatic evaluations of the mental representation of ambiguity are discussed

Clinically relevant investigation of flattening filter-free skin dose

As flattening filter-free (FFF) photon beams become readily available for treatment delivery in techniques such as SBRT, thorough investigation of skin dose from FFF photon beams is necessary under clinically relevant conditions. Using a parallel-plate PTW Markus chamber placed in a custom water-equivalent phantom, surface-dose measurements were taken at 2 × 2, 3 × 3, 4 × 4, 6 × 6, 8 × 8, 10 × 10, 20 × 20, and 30 × 30 cm2 field sizes, at 80, 90, and 100 cm source-to-surface distances (SSDs), and with fields defined by jaws and multileaf collimator (MLC) using multiple beam energies (6X, 6XFFF, 10X, and 10XFFF). The same set of measurements was repeated with the chamber at a reference depth of 10 cm. Each surface measurement was normalized by its corresponding reference depth measurement for analysis. The FFF surface doses at 100 cm SSD were higher than flattened surface doses by 45% at 2 × 2 cm2 to 13% at 20 × 20 cm2 for 6 MV energy. These surface dose differences varied to a greater degree as energy increased, ranging from +63% at 2 × 2 cm2 to -2% at 20 × 20 cm2 for 10 MV. At small field sizes, higher energy increased FFF surface dose relative to flattened surface dose; while at larger field sizes, relative FFF surface dose was higher for lower energies. At both energies investigated, decreasing SSD caused a decrease in the ratios of FFF-to-flattened surface dose. Variability with SSD of FFF-to flattened surface dose differences increased with field size and ranged from 0% to 6%. The field size at which FFF and flattened beams gave the same skin dose increased with decreasing beam energy. Surface dose was higher with MLC fields compared to jaw fields under most conditions, with the difference reaching its maximum at a field size between 4 × 4 cm2 and 6 × 6 cm2 for a given energy and SSD. This study conveyed the magnitude of surface dose in a clinically meaningful manner by reporting results normalized to 10 cm depth dose instead of depth of dose maximum

Estimate of the uncertainties in the relative risk of secondary malignant neoplasms following proton therapy and intensity-modulated photon therapy

Theoretical calculations have shown that proton therapy can reduce the incidence of radiation-induced secondary malignant neoplasms (SMN) compared with photon therapy for patients with prostate cancer. However, the uncertainties associated with calculations of SMN risk had not been assessed. The objective of this study was to quantify the uncertainties in projected risks of secondary cancer following contemporary proton and photon radiotherapies for prostate cancer. We performed a rigorous propagation of errors and several sensitivity tests to estimate the uncertainty in the ratio of relative risk (RRR) due to the largest contributors to the uncertainty: the radiation weighting factor for neutrons, the dose-response model for radiation carcinogenesis and interpatient variations in absorbed dose. The interval of values for the radiation weighting factor for neutrons and the dose-response model were derived from the literature, while interpatient variations in absorbed dose were taken from actual patient data. The influence of each parameter on a baseline RRR value was quantified. Our analysis revealed that the calculated RRR was insensitive to the largest contributors to the uncertainty. Uncertainties in the radiation weighting factor for neutrons, the shape of the dose-risk model and interpatient variations in therapeutic and stray doses introduced a total uncertainty of 33% to the baseline RRR calculation. © 2010 Institute of Physics and Engineering in Medicine

Monte Carlo calculations and measurements of absorbed dose per monitor unit for the treatment of uveal melanoma with proton therapy

The treatment of uveal melanoma with proton radiotherapy has provided excellent clinical outcomes. However, contemporary treatment planning systems use simplistic dose algorithms that limit the accuracy of relative dose distributions. Further, absolute predictions of absorbed dose per monitor unit are not yet available in these systems. The purpose of this study was to determine if Monte Carlo methods could predict dose per monitor unit (D/MU) value at the center of a proton spread-out Bragg peak (SOBP) to within 1% on measured values for a variety of treatment fields relevant to ocular proton therapy. The MCNPX Monte Carlo transport code, in combination with realistic models for the ocular beam delivery apparatus and a water phantom, was used to calculate dose distributions and D/MU values, which were verified by the measurements. Measured proton beam data included central-axis depth dose profiles, relative cross-field profiles and absolute D/MU measurements under several combinations of beam penetration ranges and range-modulation widths. The Monte Carlo method predicted D/MU values that agreed with measurement to within 1% and dose profiles that agreed with measurement to within 3% of peak dose or within 0.5 mm distance-to-agreement. Lastly, a demonstration of the clinical utility of this technique included calculations of dose distributions and D/MU values in a realistic model of the human eye. It is possible to predict D/MU values accurately for clinical relevant range-modulated proton beams for ocular therapy using the Monte Carlo method. It is thus feasible to use the Monte Carlo method as a routine absolute dose algorithm for ocular proton therapy. © 2008 Institute of Physics and Engineering in Medicine

The Protomedicato Tribunal and minorities in Castile at the end of the 17th century: the case of surgeon Roldán Solimán

[EN] This note aims to provide a small set of documents which report the vicissitudes of a North-African Muslim surgeon who tried to settle professionally during the late seventeenth century in the Kingdom of Castile. The four letters exchanged between the Royal Palace and the Castilian tribunal of the Protomedicato reveal that the Spanish king Charles II (1661-1700) resoluted supported the surgeon's aspirations, and the Protomedicato's concerted resistence to the royal will. These eloquent documents shed light on the history of the Castilian Protomedicato during the final years of the reign of the last Habsburg king in Spain by providing evidence about the role of this institution in the process of segregation/exclusion of ethnic minorities from the practice of health professions.[ES] El objeto de esta nota es presentar y editar una colección documental muy breve cuyo contenido nos informa sobre las vicisitudes de un cirujano musulmán norteafricano que a finales del siglo XVII busca su asentamiento profesional en la Corona de Castilla. Las cuatro cartas entre el Palacio Real y el Tribunal del Protomedicato, que se conservan en relación a este asunto, revelan tanto el decidido apoyo del Rey Carlos 11 (1665-1700) a las pretensiones del cirujano, como la fuerte resistencia ofrecida por el Protomedicato a la voluntad real. Esta expresiva documentación arroja luz en torno a la historia del Protomedicato en la Corona de Castilla durante los años finales del reinado del último Habsburgo en España, ilustrándonos sobre el papel entonces jugado por esta institución en el proceso de segregación/exclusión de las minorías étnicas, de la práctica de las ocupaciones sanitarias.Peer reviewe

Use of diverging apertures to minimize the edge scatter in passive scattering proton therapy

The purpose of this study was to evaluate the use of diverging-cut aperture to minimize collimator contamination in proton therapy. Two sets of apertures with nondivergent and divergent edge were fabricated to produce a 10 cm x 10 cm field at the radiation isocenter of a single-room proton therapy unit. Transverse profiles were acquired in a scanning water tank with both aperture sets. Up to 9.5% extra dose was observed from aperture scattering near the field edges with the nondivergent aperture set at 2 cm above the water surface and remained 3.0% at depth of 10 cm. For the divergent set, the contamination was reduced to less than 3.5% and 1.3%, respectively. Our study demonstrated that scattering from apertures contaminated the dose distribution near the field edge at shallow depth. A diverging-cut aperture was capable of reducing the contamination and is recommended for use in passive scattering proton therapy, especially when critical organs are lateral and proximal to the target at shallow depth